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'Restoring' old drill batteries that won't charge


reb78

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I've managed to bring two 13volt drill batteries back to life by flicking a bit of charge through them from another good battery like this chap describes here

https://m.youtube.com/watch?v=yvpGp2CM-qk

I didn't really understand how it works, but thought that was worth a try and lo and behold, it worked on two completely dead and unchargeable batteries.

Now, some of bathe YouTube vids talk about doing the same thing using a welder. Is that dangerous? Would you get a better effect than using a small battery of 13 or 18 volts? Would a car battery be better? (I had no idea so stuck with another small battery as I didn't want to blow anything up!)

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There are various videos showing different methods on you tube. I tried one with a welder a few years ago, in would then take a charge but never as good as a fresh battery and this deteriorated back to nothing. have not bothered since but have thought about it again as I have a van battery I would like to kick start.

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Have a read of this instructable Richard http://www.instructables.com/id/Revive-Nicad-Batteries-by-Zapping-with-a-Welder/ also have a read of the comments, there is some pretty good info in there.

I have done this before with AA rechargeable batteries and a bench power supply, it bought them back to life and they have been fine for a couple of years.

NB If using a welder make sure it's a DC one. Oh and make sure the battery isn't a Lithium Ion one ;)

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Barry is spot on - do not use with Lithium Ion batteries! I wouldn't recommend a welder either.

I have used the technique on NiCads and NiMH with limited success, but wouldn't recommend with any high capacity battery. The theory was that you put a semi-controlled burst of energy through the battery to burn through any shorts. That burst was supplied by discharging a capacitor charged to greater than the nominal cell voltage (6-9v for a single NiCad cell) into the battery - obviously observing polarity. That capacitor was charged via a resistor which was suitably sized to charge the cell at nominal 1/10 rate. The resistor and charging source remained connected when the capacitor was discharged through the cell via a switch. With any luck the burst of charge burnt through the short and, once the short was removed, the cell started to charge normally via the resistor.

The restored batteries were never particularly good and the self discharge rate was noticeably higher than the originals, but they served a purpose.

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